ENDOCRINE HOMEOSTASIS IN DOGS UNDER NONHYPOXIC-HYPOBARIC CONDITIONS.

Plasma insulin concentration, 17-hydroxycorticosteroid 17-OHCS secretion rate, and norepinephrine NE secretion were studied in dogs anesthetized with sodium pentobaribital and exposed to 100 oxygen at 259 torr. The 17-OHCS secretion rate was also studied in dogs breathing 100 oxygen at 760 torr. The secretion rates of NE and 17-OHCS were estimated by direct measurements on blood collected from a cannula inserted into the left lumboadrenal vein of each dog. No change was detected in plasma insulin concentration. Slight increases in NE secretion were noted in 2 of 3 dogs exposed to the low pressure. The secretion rate of 17-OHCS increased to about 25 of maximum values during exposure to 100 oxygen at 760 torr and at 259 torr. However, the values over time were different for the two pressures. Peak 17-OHCS secretion occurred after 15 minutes at 259 torr 90 minutes on 100 oxygen, but not until 135 minutes on oxygen at 760 torr. This indicates that dogs may be mildly stressed by breathing 100 oxygen and that there is a stress associated with hypobarism that cannot be attributed to hypoxia. Author